The present invention relates broadly to the field of apparatus used for extracting moisture from granular materials. More narrowly, however, it deals with dryers which function to extract moisture from grain as a consequence of vaporization to the moisture resulting from heat transfer as the grain passes downwardly through a plenum or a series of plenum modules. A specific focus of the invention is a module which is insertable in an existing dryer to more efficiently effect the drying process.
Various apparatus have been used for drying granular materials. Such apparatus are particularly useful in treating grains such as oats, rapeseed and soybeans. Moisture is removed to process a valuable foodstuff and to maximize the period of time over which the grain can be stored.
Proper processing is facilitated in other ways also. The objectives previously discussed can also be obtained, in some measure, by thermal treatment of the grain.
Depending upon the particular grain, a number of effects can be achieved. Moisture removal and heat treatment can have the effect of deactivating fat-reducing enzymes. This results in lengthening the storability of the grain. In some cases, the treatment results in the removal of bitter tastes and brings out, more effectively, pleasing flavor and aroma.
Grains, when properly treated, are heated generally evenly over a desired period of time. The time over which heating occurs is dependent upon capacity of the treating apparatus and other factors. Heating can be maintained, if desired, for several hours by regulating the rate of flow of the grain through a treating apparatus. Product temperatures can be elevated up to approximately 130xc2x0 C.
One apparatus used for drying, for example, oats has been developed by Buhler-Miag. The apparatus design employs a plurality of modules stacked vertically to define a vertically-elongated processing plenum. The grain is introduced in the uppermost module, and it passes downwardly, through a plenum formed by the stacked modules, to an egress aperture controlled by appropriate apparatus. Introduction of grain into the apparatus, proximate the top end thereof, is coordinated with discharge of the grain from the bottom so that the device is maintained in a substantially full disposition at all times.
The grain moves through the various modules as it passes downwardly through the column of interconnected modules. The time to which the grain is exposed to thermic treatment is governed by a number of factors, including the volume of grain in the apparatus and the flow rate of the product downwardly.
Each module employs a plurality of rows of staggered closed ducts extending across the modules. Staggering of the ducts in adjacent rows facilitates an even heating of the grain. The ducts are closed in cross-section, and the ducts convey steam from an inlet manifold on one side of the module to an outlet manifold on the other side of the module. One type of duct employed in the Buhler-Miag dryer is generally hexagonal in cross-section and of a generally vertically elongated configuration.
The Buhler-Miag dryer varies from other prior art devices with regard to the extent of moisture removed from the grain. Typical, however, of devices of this type known in the prior art is a removal of 0.1-0.2% of the moisture as the temperature of the grain is elevated from between 50xc2x0 F.-150xc2x0 F.
It is to these dictates of the prior art and the shortcomings thereof as discussed above that the present invention is directed. It is an improved structure, usable in combination with, for example, a Buhler-Miag dryer to increase the efficiency thereof.